One of the unique features of bacterial cells is the presence of a peptidoglycan layer that surrounds and protects the cytoplasmic membrane. Many of the best antibiotics function by inhibiting peptidoglycan biosynthesis, which ultimately leads to cell lysis. Unfortunately, resistance to existing antibiotics is a growing problem that poses a significant threat to human health. It is imperative to develop new drugs to treat bacterial infections. To facilitate this effort, structural and mechanistic information about the enzymes involved in critical biosynthetic transformations is required. The long term goal of the proposed research is to develop a detailed understanding of MurG, a GlcNAc transferase that catalyzes the last intracellular step in peptidoglycan biosynthesis. Almost nothing is currently known about the enzyme because until recently there were no direct assays to monitor MurG activity. We have developed a rapid, direct assay to quantitate MurG activity and are proposing to synthesize and evaluate various substrate analogs and inhibitors to obtain information about the topology of the active site and the enzyme mechanism. These studies will provide information that may be useful in the design of new antibiotics.